Field of the Invention
The present invention generally relates to an electronic part mounting substrate and a method for producing the same. More specifically, the invention relates to an electronic part mounting substrate wherein at least one electronic part, such as a semiconductor chip, is mounted on one side of a metal plate of aluminum or an aluminum alloy of a metal/ceramic bonding substrate wherein the other side of the metal plate is bonded to a ceramic substrate, and a method for producing the same.
Description of the Prior Art
Power modules have been used for controlling heavy-current for electric vehicles, electric railcars, machine tools and so forth. In a conventional power module, a metal/ceramic insulating substrate is fixed to one side of a metal plate or compound material called base plate, and semiconductor chips are fixed to a metal circuit plate of the metal/ceramic insulating substrate by soldering.
In recent years, it is proposed that a silver paste containing fine silver particles is used as a bonding agent to be arranged between articles to be heated for a predetermined period of time while pressing the articles against each other, to sinter silver in the bonding agent to bond the articles to each other (see, e.g., Japanese Patent Laid-Open No. 2011-80147). It is attempted that such a bonding agent is substituted for solder to fix electronic parts, such as semiconductor chips, on a metal plate of a metal/ceramic insulating substrate.
However, if the silver paste containing fine silver particles disclosed in Japanese Patent Laid-Open No. 2011-80147 is used as a bonding agent, it is not possible to obtain a sufficient bonding strength unless articles to be bonded are made of copper or plated with an expensive noble metal, such as gold, silver or palladium. For that reason, in the case of a metal/ceramic insulating substrate wherein a metal plate of aluminum or an aluminum alloy (for mounting thereon electronic parts) is bonded to a ceramic substrate, or in the case of a metal/ceramic insulating substrate wherein a metal plate of aluminum or an aluminum alloy (for mounting thereon electronic parts) is plated with nickel or a nickel alloy to be bonded to a ceramic substrate, it is not possible to use the silver paste containing fine silver particles, which is disclosed in Japanese Patent Laid-Open No. 2011-80147, as a bonding agent to bond electronic parts, such as semiconductor chips, to the metal plate (mounting thereon electronic parts) with a sufficient bonding strength.